The colon is recognized as an extremely important organ from the standpoint of both normal physiological and pathological processes. Elucidation of its plasma membranes structure would greatly aid in further understanding these processes. In addition, cell surface changes in colonic epithelial cells assume added importance in view of the greater incidence of malignant transformation of this organ. We therefore propose to first isolate colonic epithelial cells from the heterogenous population of cells found in this organ. Crypt and surface epithelial cells will also be separated. Luminal and basolateral plasma membranes will then be isolated and purified. Their biochemical composition including protein, lipid, glycoprotein and glycolipid will be analyzed. In addition, each membranes adenylate cyclase activity and "fluidity" will be determined. After this is accomplished in the "normal" rat colon animals will be treated with the procarcinogen 1,2 Dimethylhydrazine with appropriate control. Tumor epithelial cells will then be separated and their plasma mmbranes isolated. These tumor membranes will then have their biochemical composition (see above) analyzed. It is anticipated that there should be differences between the "normal" and tumor membranes composition which might further elucidate the malignant process.